kennedy elicits this blistering response from his opponent. >> senator, you're no jack kennedy. >> reporter: body language plays a part in the presidential debate in 1992, george h.w. bush deliberately looks at his watch and pays for it when the audience and voters see it as disrespectful. >> there are differences. >> reporter: body language makes a difference in a debate between al gore and george w. bush as well. gore sighs over and over again and bush surprises by winning the debate and the election. both president obama and governor romney are seasoned debaters, and expertes say neither are prone to making major gaffes. but if there is one thing that history has taught us when it comes to presidential debates, expect the unexpected. anderson cooper, cnn. >>> once again, the night is tomorrow, the president versus his challenger, face to face, special coverage begins at 7:00 eastern, right here on cnn and on cnn.com. >>> a lot more news developing this hour. watch this. america's top guy in afghanistan says he will not allow troops to be murdered. but do these insider attacks mean a chan